Navigation aids, channel markers, water-based mines, and the like, are floating objects (on the water surface or below) that are typically anchored to the bottom of a body of water in order to hold them at a fixed coordinate. Typically, such an object is attached, by means of a lanyard, to a submerged weight that resides on the bottom of the body of water. The lanyard provides a positive connection between the floating objects and the bottom of a body of water. For the purposes of this specification, including the appended claims, the term “lanyard” means a cord, a chain, a rope, a cable, or the like, which can be used to connect one object to another.
In addition, communication cables, and the like, are often deployed along the bottom of a body of water, such as an ocean, and require positive connection to the bottom at various points.
There are several methods to deploy a floating object or communications cable. A first deployment method requires that a weight is attached to a lanyard on board a ship floating on the surface of the water. The weight, with attached lanyard, is then allowed to fall through the water until it reaches the bottom. As the weight falls, the lanyard pays out from a capstan located on board the ship. During lanyard payout, an axial tension develops in the lanyard. The weight's arrival at the bottom is indicated by a decrease in this axial tension. Once the weight is determined to be on the bottom, the lanyard is clamped to preclude further lanyard payout. The floating object is then attached to the lanyard, the lanyard is cut above this attachment point, and the floating object is jettisoned overboard.
There are several drawbacks to this first method, however. First, it is a time-consuming and labor-intensive process. Second, fluctuation of underwater currents can lead to false indications that the weight has reached the bottom. Third, the process can be dangerous due to the forces that can develop when a lanyard under high axial tension is cut.
A second method for deploying a floating object utilizes a lanyard clamp that is submerged with the weight. A control line is attached to this lanyard clamp so that it can be actively actuated once it is determined that the weight has reached the bottom. In addition to having many of the same drawbacks of the first method, this method also adds cost and complexity due to the additional lanyard and lanyard handling apparatus. In addition, the added infrastructure exacerbates deck crowding on the ship, which exposes on-board personnel to additional safety hazard. Finally, fluctuation of underwater currents can cause snarling of the multiple lanyards during deployment.
There exists a need, therefore, for a weight deployment system that avoids or mitigates some or all of these problems.